1. Field of the Invention
The present invention relates to an image forming apparatus including an interchangeable engine as well as an interchangeable paper feeding and outputting system.
2. Description of the Related Art
Some image forming apparatuses including copiers and printers for performing only black and white printing or both black and white printing and color printing are known.
Also, by connecting a different apparatus to such an image forming apparatus, some image forming systems can be provided that have capabilities that otherwise could not be realized by the image forming apparatus alone.
Japanese Patent Laid-Open No. 11-292335 describes a copier formed by connecting an image reader unit to an image forming apparatus and capable of copying the image of an original document read out by the image reader unit. In addition, an image forming apparatus including a plurality of interchangeably stacked paper feeder units, which also serve as a mounting base of the image forming apparatus, has been proposed so that various types of feeder units can be used. Furthermore, some image forming apparatuses are known that are capable of being connected to a post-print processing apparatus (an accessory) that sorts or staples printed recording sheets.
Additionally, a variety of image forming apparatuses that are capable of having an optional unit attached thereto have been developed. For example, for some image forming apparatuses, although the standard functionality of the image forming apparatus is minimized, a duplex transport unit for turning over a recording sheet after one-side printing can be optionally attached to the image forming apparatuses. As noted above, by designing some units in the image forming apparatus to be removable, the image forming apparatus meets a user's specific requirements regarding usage of the image forming apparatus.
In general, a user selects an image forming apparatus that provides the functionality desired by the user, performance (such as black and white printing/color printing and the number of output pages per minute), and ease of use (such as the dimensions and the position of outputting sheets) from among various product lines of the image forming apparatus. Furthermore, when the user desires functionality and performance that are not provided by the image forming apparatus (such as duplex printing, sorting, or stapling), the user selects a configuration by, as described above, assembling an optional accessory, an optional apparatus, or an optional unit to the image forming apparatus so that the user can obtain the desired functionality and performance. By cooperating with the connected accessory, apparatus, or unit, the image forming apparatus can provide a variety of operations, which is convenient for the user.
However, the configuration and available accessories of an existing image forming apparatus are designed so that most typical users can comfortably use the image forming apparatus, and therefore, the image forming apparatus cannot flexibly provide the functionality that individual users desire.
That is, the existing image forming apparatus has a configuration so as to perform an operation in cooperation with the accessories, various apparatus, or units. Thus, the existing image forming apparatus can provide operations according to an operating mode, functionality, and performance available only in such a configuration. For example, when a feeder unit or an accessory is connected to the image forming apparatus, the total operating performance of the image forming apparatus may be limited depending on the combination of the image forming apparatus and a feeder unit (or an accessory). In addition, depending on the configuration of an image forming unit, a feeder unit, and a paper transport unit in the image forming apparatus, the total operating performance of the image forming apparatus is determined. As a result, the image forming apparatus does not flexibly provide the functionality that individual user desire.